What to consider when selecting medical device interconnects

Technology advances in electronic consumer devices and the telecommunications industry are converging at a rapid rate with medical device technology. For example, the medical industry now embraces membrane switches from the appliance industry and relies on mobile phone interconnects within portable medical monitoring devices. In addition, super-precise surgical tools have been further improved by combining advanced fiber optic and interconnect design technologies.

Converged technologies like these have not only greatly enhanced the ability of healthcare professionals to provide direct patient care in clinics and hospital settings but have also helped monitor patient conditions remotely. In today’s interconnected world, it is not unusual for healthcare professionals to consult with another healthcare professional in another city or around the globe. Increasingly, mobile communications are being used to monitor and coach patients with chronic conditions like diabetes.

Healthcare reform has also stimulated integrated approaches for patient diagnostics and real-time patient monitoring. Today’s telecommunications systems provide the super highway for managing digital information as illustrated by Picture Archival and communications systems (PACS). PACS enables images such as x-rays and scans to be stored electronically and viewed on screens, creating a near film-less process and improved diagnosis methods. Doctors and other health professionals can access and compare images at the touch of a button.

But as medical device manufacturers further improve existing products and bring new products to market that take advantage of the latest technologies, engineers face conditions unique to the medical industry that make designing and manufacturing more challenging. This is particularly true in the current economic climate, where the pressure is on to deliver healthcare more cost-effectively. Whereas medical interconnects have traditionally been supported by specialty manufacturers, industry trends are increasingly leaning towards standards from other industries, such as consumer electronics and telecommunications.

Figure 1: The medical circular lensed MT with tab

The Molex circular MT expanded beam interconnect solution shown in Figure 1 is one example of how advanced electronics are driving medical device innovations. When developing medical devices, manufacturers must consider durability and reliability to a greater degree compared to the consumer and telecommunications market. That’s because medical devices are expected to last for many years, and in cases where devices are invasive to the human body, they must perform consistently in relatively harsh environments. This is a real challenge as it relates to the use of industry-standard interconnects in the medical environment, where the form factor may be correct, but the materials and lifecycle may not match.

The need for 'modified-off-the-shelf' (MOTS) interconnects is a compromise of taking existing technology like a micro HDMI connector used in home audio/visual devices and perhaps ruggedizing it with different plating or retention features for use in medical devices. MOTS is where there is significant value for both the device designers and the interconnect providers – using prior components at an 80 percent level, for example, can replace the need for a custom interconnect. When considering MOTS, it is beneficial to work with the company’s application engineers to identify the risks and benefits of a particular interconnect solution.

The caveat is that many healthcare devices are attached on or into patients. In these cases, many medical device designers also face the extra challenge of providing functionality within small spaces with biocompatibility. In most cases, the medical device manufacturer will already have a pre-defined list of biocompatible materials that can be used. Although a part of this material definition is determined through regulatory bodies, since the responsibility of material choice relies on the device manufacturer, there can be some pretty high-spec materials included.

The human body itself is a pretty stable environment, but once non-organic materials enter it, saline, blood and high humidity levels can cause serious corrosion and leakage. These biocompatible materials must also not react or be rejected by the body, so a material that has nickel in it, for example, must be avoided as a relatively high proportion of the population are allergic to nickel.

Metal alloys are predominantly used by medical device manufacturers including cobalt chromium, titanium, MP35N and stainless steel – 316L, in particular, has been tried and tested. Titanium, a very light-weight, strong and corrosion-resistant material, is commonly used in orthopaedic medicine for a hip replacement though is very expensive. MP35N is a conductive metal alloy that is highly resistant to the corrosive elements found in the body and is widely used for invasive cardiac applications. Medical-grade silicones have also become generally accepted for applications including defibrillator pads.